The present invention relates to controlled actuator mechanisms and more particularly concerns simplified and improved control of such mechanisms.
Controlled actuator mechanisms are used in a number of different applications and are particularly useful in aircraft for initiating various types of emergency operations. Commonly, explosive charges are employed to perform emergency functions with maximum certainty and minimum delay. Thus, upon occurrence of an emergency, detonation of an explosive charge is initiated by a controlled actuator mechanism and emergency procedures such as removal of a canopy of a pilot's compartment, ejection of a pilot's seat with the pilot therein, release of restraints holding the pilot to the seat and release and deployment of a parachute for recovery of the ejected pilot are carried out. Certain of these mechanisms are mounted directly upon the parachute and may be hand operated or operated, after suitable delay, by ejection of the pilot from the aircraft.
In many of these operations, and in particular for release and deployment of the parachute, it is necessary that the desired emergency action such as deployment of the parachute, does not occur unless the pilot and his parachute are below a predetermined altitude. This is so even though the command to accomplish the emergency procedures occurs at a considerably earlier time (and at a higher altitude). Accordingly, actuators of this type must be controlled by a command, which commonly occurs when emergency procedure is desired to be initiated, and in addition, by a pressure sensitive device.
It will be understood that emergency initiators and actuators of the type under discussion, are generally used but one time. Nevertheless, they are carried about for long periods of time and for such long periods must be in continued state of readiness. This long inactive period of constant readiness considerably intensifies inherent problems.
In some prior art mechanisms, a cartridge is fired by a firing pin that is powered by a stressed spring and retained by an aneroid cell. The device is assembled in cocked position and thus additional safety devices must be provided to prevent premature firing of the explosive cartridge. Even with the use of such safety devices, the continual presence in an aircraft of a cocked or armed explosive device is highly undesirable.
In those devices of the prior art that are barometrically controlled, the sensitive pressure responsive aneroid generally is directly connected to a trigger mechanism as by a pin connection or the like. This connection imposes a continuous load upon and restraint against the ordinary motion of the sensitive pressure instrument. Continual motion of the aneroid device as it is carried about through varying ambient pressures causes repetitive motion of devices connected thereto. This long period of continued motion of interconnected elements of trigger mechanisms is not desirable and may significantly degrade reliability.
One solution to the danger of a pre-cocked explosive initiator is suggested in U.S. Patent to Roberts et al U.S. Pat. No. 3,142,958, wherein a parachute release mechanism is operated by the firing of an explosive charge. Detonation of the charge is initiated by a firing mechanism that is cocked or armed as an incident to the generation of power in a pilot's seat ejector mechanism. When the seat ejection mechanism is actuated, power is supplied to the parachute release initiator to move a firing pin and a hammer against the action of a firing spring into a cocked position. As the firing pin and hammer are moved to the cocked position in this arrangement an aneroid controlled sear pin is pivoted and the hammer is thereby moved into engagement with the sear pin. The sear pin is held until the aneroid operates the trigger mechanism to release restraint on the sear and allow the hammer and firing pin to be driven under the action of the compressed spring. In the arrangement of this patent, the aneroid control element is at all times connected to the sear restraining trigger and consequently the trigger mechanism is continually moving throughout the inactive life of the device. Further, cocking of the device requires a relatively complex interaction and motion of the sear and hammer since the latter is no way connected with the sear pin prior to cocking, and the sear must be pivoted in the one direction to permit the hammer to move into its restraining engagement with the sear. Motion of the sear in the opposite direction is then required for release of the hammer for firing. The arrangment of Roberts et al, does not facilitate a compact minimum volume package with the barometer in line with the firing pin. Thus, size and weight of the device are undesirably increased.
A parachute actuator is shown in the patent to Hallerberg, U.S. Pat. No. 2,953,063 wherein a leaf spring drives a firing pin having a secondary control from an aneroid device via a system of levers pivoted to and between the hammer and to the aneroid device. A major drawback of the arrangement of Hallerberg is the fact that the firing spring and hammer must be precocked so that the firing spring is always stressed and the aircraft is required to continuously carry an armed and cocked explosive device. Not only is the device of Hallerberg always cocked or armed, but the aneroid is directly connected at all times to the lever system and thus this system of levers must move whenever the aneroid experiences variations in ambient pressure.
In a copending application of F. X. Chevrier et al for Controlled Actuator, Ser. No. 491,733, filed July 25, 1974, there is described an aneroid actuated explosive initiator which is cocked in response to a relatively high pressure generated by an emergency device. The actuator of the co-pending application Ser. No. 491,733 is operable under high pressure, in the order of 400 pounds per square inch, for example, and embodies a spring driven rotatable sear for restraining the cocked hammer in response to ambient pressure. Relatively large cocking forces and unique packaging requirements are involved. At least in part because of the smaller forces required for operation of a parachute rip cord release, a simpler and more directly operable mechanism and aneroid controlled sear configuration can be used and are desirable.
Accordingly, it is an object ot the present invention to provide a controlled actuator that eliminates or minimizes the above-mentioned disadvantages and achieves efficient, safe, reliable and precision operation in a compact package of small size and weight.